1. Field of the Invention
The present invention generally relates to agricultural implements, and more particularly to implements having frames which fold for transport and unfold for field use.
2. Description of the Related Art
It is common practice for agricultural implements to be made with frames having three sections; a center section and two folding sections which are pivotally connected to the center section on opposed sides thereof. The folding sections are moveable between a generally horizontal working position and a generally vertical transport position which allows the implement to be towed through relatively narrow passages, such as gates between fields, and along public roads. In the working position, the folding sections are usually allowed to flex relative to the center section in order to more accurately follow the contours of the ground. A plurality of ground working tools are attached to each of the frame sections. Each section further includes one or more hydraulically controlled lift wheel assemblies which control the depth of cut of the ground working tools and allow the respective section to follow the terrain.
As implements of this type increase in working width, the height of the implement in the transport position can become problematic. If the folding sections are too tall, it becomes difficult to maneuver the implement under obstacles such as tree limbs and overhead utility lines. The implement can also become top-heavy and prone to tip over if the folding sections is disproportionately tall relative to the width of the center section.
One common solution to this problem is to simply increase the number of independently flexible frame sections in the implement from three to five. The two outermost sections can then be folded back over the center section, decreasing the transport height of the implement. The main problem with implements of this type is that they are relatively expensive to manufacture. Each independently flexible frame section requires a separate set of lift wheel assemblies, along with the hydraulic actuators and mechanical linkages required to operate them.
A second approach to the problem is to provide each of the folding sections with a short extension sections that folds for transport but remains rigid relative to the respective folding section in the field. The extension sections do not require their own lift wheel assemblies because they do not flex relative to the adjacent folding section. A problem with implements of this type is that the extension sections hang out past the nearest lift wheel assemblies, which are located on the adjacent folding sections, and therefore do not follow the terrain closely. This results in the ground working tools on the extension sections having an inconsistent depth of cut.
What is needed is a folding agricultural implement frame which provides an implement that is of an acceptable height in the transport position, and which provides good depth control for the ground working tools without the expense of having additional independently flexible frame sections.
The present invention is a folding agricultural implement of the type having a frame comprising a plurality of frame sections, the frame sections being moveable between a working position wherein said frame sections are arrayed generally side by side and a folded transport position. The frame sections include at least one inner or center section, a pair of intermediate sections positioned laterally outwardly from the inner section, and a pair of end sections positioned adjacent to the intermediate sections and outwardly therefrom. The inner section and the end sections of the implement are equipped with hydraulically adjustable lift wheel assemblies which serve to raise and lower the implement relative to the ground. The intermediate sections are not equipped with their own lift wheel assemblies.
The joints between the end sections and the intermediate sections of the implement frame are designed so that each end section is held rigid relative to the adjacent intermediate section when the implement is in the working position, but can still be folded to move the implement into the transport position. This selectively rigidity between the end sections and intermediate sections allows the intermediate sections to be supported by the lift wheel assemblies on the end sections when the implement is in the working position while preventing the joints between the sections from sagging. The desired rigidity is provided by fold linkages, each of which comprise first and second links, the first link having a first end pivotally connected to an intermediate frame section and a second end; the second link having a first end pivotally connected to the first link second end and a second end pivotally connected to the adjacent end section. A linear actuator is connected between one of the frame sections and one of the links for folding the end section relative to the intermediate section.
When the implement is in the working position, the actuator holds the first and second links in a position wherein they are generally linearly aligned to over-centered with respect to one another. In this position, the fold linkages cooperate with the actuators to hold the end sections rigid relative to the intermediate sections and prevent the outer joints from sagging. The linkages take part of the pressure off of the respective actuators so that the actuators are not solely responsible for holding the respective joints rigid.
Because the implement does not have lift wheel assemblies mounted on the intermediate sections, the usual outside-section-to-inside section method of folding an implement is not preferable. If the end sections were raised first relative to the intermediate sections, neither the end sections nor the intermediate sections would be supported, and the combined weight would cause the joints between the inner sections and the intermediate sections to sag. In order to alleviate this problem, the implement folds in different fashion than is the norm; the intermediate sections and end sections are first raised together relative to the inner section. After the intermediate sections and end sections reach a generally vertical position, the end sections are then folded downwardly over the inner section.